Digital phase locked loop having insensitive jitter characteristic for operating circumstances

Abstract

Disclosed are a phase locked loop (PLL) of a digital scheme and a method thereof. More specifically, disclosed are a digital phase locked loop having a time-to-digital converter (TDC), a digital loop filter (DLF), and a digitally controlled oscillator (DCO), and that is designed to have a constant jitter characteristic at all times even though an operating condition of a circuit varies according to a process, voltage, temperature (PVT) change, and a method thereof.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application claims priority to and the benefit of Korean Patent Application No. 10-2010-0134034 filed in the Korean Intellectual Property Office on Dec. 23, 2011, the entire contents of which are incorporated herein by reference.TECHNICAL FIELD[0002]The present invention relates to a phase locked loop (PLL) of a digital scheme, and more particularly, to a digital phase locked loop that is designed to have a constant jitter characteristic at all times even though an operating condition of a circuit varies in response to a process, voltage, temperature change (hereinafter, abbreviated as “PVT change”).BACKGROUND ART[0003]In general, a phase locked loop (generally, abbreviated as “PLL”) is a circuit that receives a reference frequency signal from the outside, and receives a frequency signal which is generated in the circuit and thereby output through a negative feedback loop, and controls the input two frequency signals to be output as ...

AI Technical Summary

Benefits of technology

[0018]The present invention has been made in an effort to provide a digital phase locked loop having a constant jitter characteristic at all times by estimating a change in a characteristic of a DCO when the characteristic of the DCO changes according to the PVT change, and by adjusting a coefficient value of a digital loop filter (DLF) to reduce the whole loop-dynamics change according to the change in the DCO characteristic.

Problems solved by technology

The characteristic of the loop filter or the frequency gain characteristic of the VCO sensitively varies according to a process, voltage, temperature (PVT) change and thus, it is not easy to configure the jitter characteristic of the phase locked loop as accurately as a designer desires.

Images